The present invention relates generally to microfabrication techniques. More particularly, the invention provides a method and device for manufacturing a beam structure composed of a polymer based material using a micromachining method and apparatus. Merely by way of example, the invention has been applied to the manufacture of a polymer based beam structure for spring applications. But it would be recognized that the invention has a much broader range of applicability. For example, the invention can be applied to micro-electro-mechanical systems, which includes, accelerometers, seismic sensors, optical switching devices, and others.
A Micro-Electro-Mechanical System, commonly called MEMS, is generally a batch-fabricated (microfabricated) system that includes both electrical and mechanical elements. MEMS elements often have characteristic sizes ranging from nanometers to millimeters. MEMS often makes possible certain systems that are smaller, faster, more economical, and energy efficient in some cases. In a general MEMS system, the electrical portion includes integrated circuits, which forms the the thinking part, while the electro-mechanical portion works with the thinking part to control functions and perception.
MEMS generally includes microsensors and actuator devices. Microsensors often gather outside information such as thermal, biological, optical, gravitational, and others. Actuators often respond to user based information to control their environment. As merely an example, mechanical transducers are common examples of MEMS. Such transducers often convert mechanical movement characteristics into electrical characteristics, which are processed. Conventional mechanical transducers are often plagued with limitations for certain applications. Mechanical sensitivity is often difficult to achieve using conventional MEMS based transducers. Here, sensitivity to mechanical force should exist in the direction of interest, but it should be fairly rigid in the other two perpendicular directions to reduce and possibly minimize mechanical cross talk. High aspect ratio structures have been proposed to form sensitive mechanical transducers.
Deep reactive ion etching (DRIE) of silicon substrate was generally used to fabricate high aspect structures for MEMS. An example of DRIE of single crystal silicon has been demonstrated by the BOSCH process, See, Ayon, A. A., Braff, R., Lin, C. C., Sawin, H. H., and Schmidt, M. A., “Characterization of a time multiplexed inductively coupled plasma etcher,” J. Electrochem. Soc., 146, (1999), pp 339-349. Other techniques to form high aspect ratio structures used polycrystaline silicon. Unfortunately, many limitations exist in using silicon based materials for high aspect ratio structures. These materials are often brittle and difficult to work with for certain applications. Additionally, the brittle material is often prone to breakage and has other limitations.
Still other conventional techniques rely upon metal materials, which would use X-ray processing. X-ray processing tends to be expensive, which leads to inefficiencies. Moreover, the conventional materials of these technologies have a large Young's modulus on the order of 100 GPa, which cannot be used for a variety of soft structure applications. Accordingly, embossing processes have been proposed to make soft structures for high aspect ratio devices. Embossing also has limitations. Embossing is often difficult to control precisely. Difficult control does not lend itself to forming high aspect ratio devices for MEMS. These and other limitations can be found throughout the present specification and more particularly below.
From the above, it is seen that techniques for manufacturing improved MEMS devices is highly desirable.